GENERATION OF LIPASES WITH DIFFERENT SPECIFICITIES ANDFUNCTIONALITIES IN BAKING

摘要

Lipases with activity towards non-polar flour lipids have been known in the baking industry for several years, where they have been used to improve dough machineability, bread volume, and crumb structure [1]. However, the use of lipases which also possess activity towards polar flour lipids is new to the baking industry. The advantageous effects of such lipases have been reported over the last few years [2,3], and in 2001 the first lipase with broad substrate specificity was brought to the market [4]. This cloned lipase, which originates from Fusarium oxysporum, provides an alternative to traditionally used dough stabilising emulsifiers such as Datem (diacetylated tartaric acid esters of monoglycerides) and SSL (sodium stearoyl-2-lactylate).Polar flour lipids are known to play a crucial role in dough stability and processing tolerance of yeast leavened bakery products, The ability of the polar flour lipids to form lipid monolayers at the gas/liquid interphase is believed to positively influence the gas retention in the dough. Further, the interaction between polar flour lipids and gluten proteins may play an important role in gas retention [5,6]. hospholipids, such as phosphatidyl choline (PC), and galactolipids, such as digalactosyl-diglycerides (DGDG) are predominant among the non-starch polar flour lipids [7]. The Fusarium oxysporum lipase, which has activity towards both polar and non-polar flour lipids, will convert PC and DGDG into even more polar components, such as lyso-phosphatidyl choline (LPC) and digalactosyl-monoglyceride (DGMG) (Figure 1).Although the Fusarium oxysporum lipase has proven to be very advantageous in the baking industry, a complete understanding of the relationship between lipase specificity and functionalityin baking is still lacking. A range of wild type enzymes with activity towards polar flour lipids have been evaluated in baking. However, only few of these improved dough stability significantly. In order to investigate this relationship further, a rangeof protein engineered enzymes were evaluated. A traditional 1,3-specific lipase from Thermomyces lanuginosus was converted into lipases with activity towards phospholipids and galactolipids by PCR techniques [8]. These lipase variants were generated torepresent a high diversity in specificity and activity, and were therefore useful for studying the link between specificity